Slotted metal pipes, or tubulars as they are often known, have been used for a considerable length of time in oil, gas and water wells as a means to limit the amount of sand or debris allowed to enter the tubular as oil, gas or water is drawn in from surrounding underground formations. The slotted tubulars effectively act as a liner and screening mechanism to permit the desired fluid to be drawn into the tubular for extraction while excluding sand, rock and other particles. Tubular liners must have slots that are sufficiently small in width to prevent particulate matter from entering the pipe, while maintaining sufficient structural integrity to withstand pressures to which they may be subjected in underground environments, particularly in wells having horizontal components.
The difficulty encountered with slotted tubulars is not so much in their use but in their method of manufacturing. The particular underground formation within which the tubular is to be deployed will for the most part dictate a maximum slot width that will be acceptable. In oil and gas well applications, it is often the case that the oil or gas being targeted is located in formations comprised of fine sand particles. In such situations it is not unusual to require a slot width in the tubular of 0.010 of an inch, or less. Unfortunately, conventional manufacturing equipment is rarely capable of cutting slots in tubulars effectively having a width less than 0.015 inches. As a result, manufacturers commonly subject slotted tubulars to a secondary seaming process where rollers are used to apply pressure to the tubular in the vicinity of the slot, having the result of narrowing the slot width at the exterior surface and forming a slot with a keystone, parabolic, or similar shaped profile.
A variety of different seaming methods have been proposed by others as a means to reduce the width of slots formed in tubulars through conventional mechanical methods. Such methods include those described under U.S. Pat. No. 6,112,570, dated Sep. 5, 2000; Canadian patent 2,183,032, dated Jul. 17, 2001; and, Canadian patent 2,324,730, dated Aug. 12, 2003.
Although the seaming methods that have been used by others have been generally successful, they also suffer from a number of inherent limitations. First, the alignment of seaming equipment with the slots or openings has proven to be difficult and often requires considerable operator effort and skill. To reduce the need for precise alignment of the seaming equipment with the slots or openings some have suggested passing the seaming equipment or rollers over the entire surface of the product in a helical pattern. While doing so may to a large degree alleviate alignment issues, it also significantly slows down the seaming process since the entire exterior surface of the product must be treated. Currently available methods also provide no mechanism for continuously checking the degree to which the width of the slots or openings have been reduced, or to accurately track instances where treated slots or openings do not meet specifications. Under existing methods, and with currently available equipment, the treated products are typically inspected manually and then manually sent back to the seaming process if it is determined that their slots are not within specified tolerances.